Abstract
Background:
The anterolateral thigh (ALT) flap is a versatile option for reconstructive surgery due to the availability of multiple tissue types and minimal donor-site morbidity. However, donor-site seroma formation remains a poorly understood complication, particularly with regard to its severity. In this study, we aimed to investigate the incidence, severity, and factors associated with seroma formation after ALT flap harvesting.
Methods:
We conducted a retrospective analysis of 150 patients who underwent ALT flap harvest between November 2020 and September 2023. Donor-site seromas were graded using the Clavien–Dindo classification, and patients were divided into 2 groups based on the presence or absence of seromas. Logistic regression analysis was performed to identify independent factors associated with seroma formation.
Results:
Seroma formation occurred in 18.0% of patients. Most cases (70.4%) were classified as Clavien–Dindo grade 1, requiring only conservative management, whereas 29.6% (5.3% of all patients) were classified as grade 3a or higher, necessitating surgical intervention. Male sex (odds ratio, 3.11; 95% confidence interval, 0.97–9.98; P = 0.039) and fascia lata harvest larger than the skin paddle area (odds ratio, 2.93; 95% confidence interval, 1.26–6.82; P = 0.017) were identified as independent factors associated with seroma formation.
Conclusions:
Fascia lata harvests larger than the skin paddle were associated with donor-site seroma formation with ALT flap harvests. Preoperative planning and careful fascia lata harvesting techniques are recommended to minimize complications.
Takeaways
Question: What factors are associated with seroma formation after anterolateral thigh (ALT) flap harvesting?
Findings: In a retrospective study of 150 patients, logistic regression analysis identified male sex and fascia lata harvest larger than the skin paddle as independent factors associated with seroma formation.
Meaning: Larger fascia lata harvests may increase the risk of donor-site seroma formation after ALT flap harvesting and should be carefully considered during preoperative planning and postoperative management.
INTRODUCTION
The anterolateral thigh (ALT) flap was first described by Song et al1 in 1984 and has since become a widely used reconstructive technique. This flap offers versatility as it can be harvested not only with the skin and subcutaneous tissue but also with the fascia lata, vastus lateralis muscle, or femoral nerve. Therefore, it can be used to reconstruct various tissue defects and is an important option in all regions such as extremities, abdominal wall, and head and neck.2–4
The ALT flap has few complications at the donor site, with paresthesia of the lateral thigh being the most common.5 Although thigh compartment syndrome and postoperative gait dysfunction are often mentioned as serious complications, in practice, the effect of vastus lateralis muscle harvesting on lower extremity function is considered to be minimal.6,7
Donor-site seroma formation after ALT flap harvest has been reported to occur in 0%–13% of patients and is a relatively minor complication.8–10 No previous reports have focused on seroma formation, and the cause and associated factors are unknown. In particular, no previous studies have analyzed seroma formation based on severity using standardized classification systems.
Through follow-up of patients who underwent ALT flap harvest at our hospital, we hypothesized that seroma would occur more frequently in patients in whom the flap was harvested with fascia lata than in those without it. To prove this hypothesis, we investigated the incidence, severity, and factors associated with seroma formation.
METHODS
We conducted a retrospective single-center case–control study. Study participants included 150 consecutive patients who underwent free ALT flap harvest between November 2020 and September 2023. Data regarding patient background, medical history, life history, the characteristics of the ALT flap, and donor-site seroma formation were extracted from the medical record databases. Characteristics of the ALT flap included donor-site laterality, skin paddle width, fascia lata harvest area, and vastus lateralis muscle harvest. The fascia lata harvest area was dichotomized as equal to or larger than versus smaller than the skin paddle area (Fig. 1). Donor-site seroma formations were graded according to the Clavien–Dindo (C–D) classification.11,12 The severity of the seroma was graded according to the treatment required, as follows: grade 1, compression or needle aspiration; grade 2, not defined for seroma; grade 3a, surgery under local anesthesia; and grade 3b, surgery under general anesthesia.
Fig. 1.
Fascia lata harvest area in ALT flaps. Dotted lines on the back indicate the fascia lata. A and B, The fascia lata harvested was smaller than the skin paddle area. Only 1 cm of fascia surrounding the perforator was included. C and D, The fascia lata harvested was larger than the skin paddle area.
We generally avoided primary fascial closure to prevent the development of compartment syndrome. A single drain was placed into the intermuscular space via a subcutaneous route. The drain was removed as soon as the patients began ambulation and the daily drainage fell to less than 20 mL, with a maximum placement duration of 2 weeks. Seroma was diagnosed by palpation.
Ethical approval to conduct this study was obtained through the institutional review board (approval no. J2024-47-2024-1). The requirement for patient informed consent was waived owing to the retrospective nature of the study.
Statistical Analysis
All statistical analyses were performed using JMP Pro version 17.0.0 (SAS Institute Inc., Cary, NC). Continuous variables were presented as mean (SD, range). All patients were categorized into 2 groups: those with and without postoperative donor-site seroma formation. The Fisher exact probability test was used to compare proportions of categorical variables (such as sex), and the Student t test was used to compare means of continuous variables (such as age) between the groups. All tests were 2-tailed, and a P value of less than 0.05 was considered statistically significant. Logistic regression analysis was performed based on the comparison of both groups to rule out confounding factors. Variables with a P value of less than 0.05 were selected as explanatory variables.
RESULTS
The details of the cohort are presented in Table 1. The study included 101 men and 49 women, with a mean age of 63.9 (12.9, 26–84) years. The overall BMI was 22.4 (4.19, 14.4–38.0) kg/m2, with 22.6 (3.97, 14.4–37.8) kg/m2 for men and 22.0 (4.62, 14.7–38.0) kg/m2 for women (P = 0.21). Among the patients, 62 (41.3%) had hypertension, 18 (12.0%) had diabetes, and 98 (65.3%) had a smoking habit. Most patients were men and had a history of smoking, and the majority underwent reconstructive surgery after resection of a malignant head and neck tumor.
Table 1.
Patient Characteristics (N = 150)
| Characteristics | n (%), Mean (SD, Range) |
|---|---|
| Sex | |
| Male | 101 (67.3) |
| Female | 49 (32.7) |
| Age, y | 63.9 (12.9, 26–84) |
| BMI, kg/m2 | 22.4 (4.19, 14.4–38.0) |
| Comorbidity | |
| Hypertension | 62 (41.3) |
| Diabetes | 18 (12.0) |
| Smoking habit | 98 (65.3) |
BMI, body mass index.
The characteristics of the harvested ALT flaps are presented in Table 2. Forty-five flaps (30%) were harvested from the left side and 105 (70%) from the right side. The mean skin paddle width was 7.10 (1.57, 4–17) cm. The fascia lata was included in 56 flaps (37.3%) with a size larger than the skin paddle and in 94 flaps (62.7%) with a size smaller than the skin paddle. The vastus lateralis muscle was included in 11 flaps (7.3%). Donor sites were primarily closed in 142 (94.7%) patients and closed by skin grafting in 8 (5.3%) patients. The fascia lata was primarily closed in 10 (6.7%) patients. Donor-site seroma formation occurred in 27 (18.0%) patients.
Table 2.
Characteristics of Anterolateral Thigh Flap (N = 150)
| Characteristics | n (%), Mean (SD, Range) |
|---|---|
| Donor-site laterality | |
| Left | 45 (30.0) |
| Right | 105 (70.0) |
| Skin paddle width, cm | 7.10 (1.57, 4–17) |
| Fascia lata area | |
| ≥Skin paddle area | 56 (37.3) |
| <Skin paddle area | 94 (62.7) |
| Harvest with vastus lateralis muscle | |
| Yes | 11 (7.3) |
| No | 139 (92.7) |
| Donor-site closure | |
| Primary closure | 142 (94.7) |
| Skin grafting | 8 (5.3) |
| Primary closure of fascia | |
| Yes | 10 (6.7) |
| No | 140 (93.3) |
| Donor-site seroma | |
| Yes | 27 (18.0) |
| No | 123 (82.0) |
The comparison between groups with and without donor-site seroma formation is summarized in Table 3. The distribution of C–D grades of seroma in the seroma group of 27 patients was as follows: grade 1 in 19 (70.4%) patients, grade 3a in 6 (22.2%) patients, and grade 3b in 2 (7.4%) patients. Grade 3b was due to massive wound margin necrosis or compartment syndrome, which required debridement, resuturing, or negative pressure wound therapy (NPWT). The incidence of C–D grade 3a or higher seroma requiring surgical intervention was 5.3% (8 of 150) of all patients. Significant differences between the 2 groups were found in sex (P = 0.040), fascia lata harvest area (P = 0.015), and vastus lateralis muscle harvest (P = 0.028). No significant differences were found in other variables.
Table 3.
Univariate Analysis of Patient and Flap Characteristics Between Groups With and Without Donor-site Seroma
| Variables | Without Seroma (N = 123), n (%), Mean (SD, Range) | With Seroma (N = 27), n (%), Mean (SD, Range) | P |
|---|---|---|---|
| Sex | 0.040* | ||
| Male | 78 (63.4) | 23 (85.2) | |
| Female | 45 (36.6) | 4 (14.8) | |
| Age, y | 63.2 (13.6, 26–84) | 66.7 (8.56, 47–79) | 0.20 |
| Preoperative BMI, kg/m2 | 22.6 (4.12, 14.4–38.0) | 21.4 (4.40, 15.0–32.6) | 0.21 |
| Comorbidity | |||
| Hypertension | 49 (39.8) | 13 (48.2) | 0.52 |
| Diabetes | 14 (11.4) | 4 (14.8) | 0.74 |
| Smoking habit | 78 (63.4) | 20 (74.1) | 0.37 |
| Donor-site laterality | 0.65 | ||
| Left | 36 (29.3) | 9 (33.3) | |
| Right | 87 (70.7) | 18 (66.7) | |
| Skin paddle width, cm | 7.06 (1.53, 4–17) | 7.30 (1.73, 4–13) | 0.48 |
| Fascia lata area | 0.015* | ||
| ≥Skin paddle area | 40 (32.5) | 16 (59.3) | |
| <Skin paddle area | 83 (67.5) | 11 (40.7) | |
| Harvest with vastus lateralis muscle | 0.028* | ||
| Yes | 6 (4.9) | 5 (18.5) | |
| No | 117 (95.1) | 22 (81.5) | |
| Donor-site closure | 0.64 | ||
| Primary closure | 117 (95.1) | 25 (92.6) | |
| Skin grafting | 6 (4.9) | 2 (7.4) | |
| Primary closure of fascia | |||
| Yes | 9 (7.3) | 1 (3.7) | 0.50 |
| No | 114 (92.6) | 26 (96.3) | |
| C–D grade of seroma | |||
| 1 | n/a | 19 (70.4) | |
| 2 | n/a | 0 | |
| 3a | n/a | 6 (22.2) | |
| 3b | n/a | 2 (7.4) | |
P < 0.05.
n/a, not applicable.
To identify factors associated with donor-site seroma, logistic regression analysis was performed using sex, fascia lata harvest area, and vastus lateralis muscle harvest as explanatory variables (Table 4). Two factors were identified as being associated with seroma formation: male sex (odds ratio, 3.11; 95% confidence interval, 0.97–9.98, P = 0.039) and fascia lata harvest larger than the skin paddle area (odds ratio, 2.93, 95% confidence interval, 1.26–6.82, P = 0.017). The risk factors for each C–D grade (1, 3a, 3b) are presented in Table 5.
Table 4.
Multivariate Analysis of Factors Associated With Donor-site Seroma
| Variables | OR | 95% CI | P |
|---|---|---|---|
| Male | 3.11 | 0.97–9.98 | 0.039* |
| Fascia lata area ≥ skin paddle area | 2.93 | 1.26–6.82 | 0.017* |
| Harvest with vastus lateralis muscle | 2.07 | 0.54–7.89 | 0.18 |
P < 0.05.
CI, confidence interval; OR, odds ratio.
Table 5.
Risk Factors for Seroma Formation Stratified by C–D Grade (1, 3a, 3b)
| Variables | C–D 1 (N = 19) | C–D 3a (N = 6) | C–D 3b (N = 2) | P |
|---|---|---|---|---|
| Sex | 0.83 | |||
| Male | 16 | 5 | 2 | |
| Female | 3 | 1 | 0 | |
| Fascia lata area | 0.40 | |||
| ≥Skin paddle area | 10 | 5 | 1 | |
| <Skin paddle area | 9 | 1 | 1 |
DISCUSSION
In this study, donor-site seroma formation occurred in 18.0% of patients, with 70.4% classified as C–D grade 1, which required no treatment. On the other hand, seromas of C–D grade 3a or higher requiring treatment occurred in 5.3% of patients. Male sex and fascia lata harvest larger than the skin paddle area were identified as being independently associated with seroma formation by logistic regression analysis. This finding regarding fascia lata harvest provides novel insights into the existing literature on donor-site complications after ALT flap harvest.
Donor-site seroma formation after ALT flap harvest has previously been reported to occur in 0%–13% of patients.8–10 However, those reports did not focus on seroma formation among donor-site complications, and the definition of seroma was unclear and was not graded according to severity. A key strength of our study is the use of the C–D classification system to assess both the incidence and severity of seroma formation, providing a framework for future studies. Although suprafascial flap dissection, small skin paddle width, and preservation of the fascia lata or a major motor branch of the femoral nerves have been reported to minimize donor-site complications,6,7,13 we could not find any reports that focused on the factors associated with seroma formation after ALT flap harvesting.
Among flaps other than the ALT, the latissimus dorsi (LD) flap has a higher incidence of donor-site seroma formation, reported at 20%–79%.14–20 Age, obesity, and flap weight were reported to be associated with seroma formation in LD flap donor sites,14–17,19,20 whereas neither age nor obesity was associated with donor-site seroma in this study. Weight data for the ALT flap were not available for this study. Schwabegger et al21 described the friction of the wound layers as the cause of the high incidence of donor-site seroma formation after LD flap harvest. Similarly, our findings suggest that fascia lata harvest may disrupt the lubricant adipofascial system,22 increasing friction between the subcutaneous tissue and the vastus lateralis or rectus femoris muscles, contributing to seroma formation.
The factors associated with donor-site seroma formation after ALT flap harvest identified in this study could provide valuable insight into minimizing donor-site complications of the widely used ALT flap reconstruction. Two primary methods exist for identifying skin perforators in ALT flap harvesting: (1) identifying perforators above the fascia lata before incising it to minimize the harvest area (a more technically challenging approach) and (2) incising the fascia lata first to locate perforators below, which simplifies perforator identification but requires a larger fascia lata harvest. In most cases, we use the suprafascial technique unless the fascia lata is needed for reconstruction or the perforators are too thin or cannot be identified above the fascia lata. Our findings indicate that seroma formation is more likely with the second method or when the fascia lata is largely involved in the flap, such as in abdominal wall reconstruction. Careful reconstructive planning is important, taking into account the difficulty of flap harvesting procedures, the necessity of fascia lata as a reconstructive material, and the impact on the donor site.
Donor-site seroma is often overlooked because of the rarity of severe cases, but seroma formation after LD flap harvesting has been reported to be associated with delayed wound healing and prolonged hospital stays.19 No studies have reported an association between donor-site seroma formation and fascia lata harvest after ALT flap harvesting. Fascia lata harvest may have been associated with donor-site seroma formation in other studies if they had focused on the association between them. Based on the results of this study, we strictly applied postoperative donor-site wound compression with elastic bandages for at least 2 weeks in patients undergoing fascia lata harvest. Furthermore, patients were informed preoperatively that the risk of seroma may be higher than usual in cases requiring fascia lata harvest.
Quilting techniques and progressive tension sutures have been reported to be effective in preventing seroma formation during LD flap harvesting.19,23 Incisional NPWT has also been reported to reduce donor-site seroma formation after LD flap harvest.24 Although incisional NPWT has been reported to reduce overall donor-site complications for ALT flaps,25,26 its specific impact on seroma formation requires further investigation. Neither quilting sutures nor NPWT was used in this study, but may be considered in cases involving fascia lata harvest.
This study has some limitations. First, the retrospective design of the study and the single-center data limit generalizability. Future prospective studies with larger, more diverse cohorts are warranted to validate our findings and refine preventive strategies. Second, although male sex was identified as an independent factor associated with seroma formation, it is a nonmodifiable variable. Its association may reflect underlying anatomical or physiological differences—such as muscle volume or subcutaneous tissue thickness—that were not directly measured in this study. Accordingly, we chose to focus our discussion on fascia lata harvest size, as it represents a modifiable and clinically actionable factor for surgical planning. Third, the size of the harvested fascia lata was not directly measured, nor was the volume of the seroma. Fourth, the vastus lateralis muscle was harvested in only 11 cases, highlighting the need for further studies with larger sample sizes to determine whether it serves as a true confounding factor.
CONCLUSIONS
Fascia lata harvest larger than the skin paddle was independently associated with donor-site seroma formation after ALT flap harvest. Preoperative planning and postoperative management should consider this factor, and careful fascia lata harvesting techniques are recommended to minimize complications.
DISCLOSURE
The authors have no financial interest to declare in relation to the content of this article.
ACKNOWLEDGMENT
The authors would like to thank Editage (www.editage.jp) for English language editing.
Footnotes
Published online 27 August 2025.
Presented at the 67th Annual Meeting of the Japanese Society for Plastic and Reconstructive Surgery, April 10–12, 2024, Kobe, Japan.
Disclosure statements are at the end of this article, following the correspondence information.
The datasets generated and analyzed during the current study are available from the corresponding author upon reasonable request.
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